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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Sat Nov 24 17:57:37 2007" /> 9 <meta name="created" content="Wed Nov 28 19:29:25 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
15<h3 id="TOP">Index</h3> 15<h3 id="TOP">Index</h3>
16 16
17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 20<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 21<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 22<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> 23<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> 24<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
… …
31<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li> 32<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
32<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> 33<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
33<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> 34<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
34<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li> 35<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
35<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> 36<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
37<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li>
36<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li> 38<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
37<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li> 39<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
38<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> 40<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
41<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li>
39</ul> 42</ul>
40</li> 43</li>
41<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 44<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
42<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> 45<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
43<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> 46<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
47<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li>
44<li><a href="#EMBEDDING">EMBEDDING</a> 48<li><a href="#EMBEDDING">EMBEDDING</a>
45<ul><li><a href="#FILESETS">FILESETS</a> 49<ul><li><a href="#FILESETS">FILESETS</a>
46<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> 50<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
47<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> 51<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
48<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> 52<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
… …
50</li> 54</li>
51<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li> 55<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
52<li><a href="#EXAMPLES">EXAMPLES</a></li> 56<li><a href="#EXAMPLES">EXAMPLES</a></li>
53</ul> 57</ul>
54</li> 58</li>
59<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
55<li><a href="#AUTHOR">AUTHOR</a> 60<li><a href="#AUTHOR">AUTHOR</a>
56</li> 61</li>
57</ul><hr /> 62</ul><hr />
58<!-- INDEX END --> 63<!-- INDEX END -->
59 64
60<h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> 65<h1 id="NAME">NAME</h1>
61<div id="NAME_CONTENT"> 66<div id="NAME_CONTENT">
62<p>libev - a high performance full-featured event loop written in C</p> 67<p>libev - a high performance full-featured event loop written in C</p>
63 68
64</div> 69</div>
65<h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> 70<h1 id="SYNOPSIS">SYNOPSIS</h1>
66<div id="SYNOPSIS_CONTENT"> 71<div id="SYNOPSIS_CONTENT">
67<pre> #include &lt;ev.h&gt; 72<pre> #include &lt;ev.h&gt;
68 73
69</pre> 74</pre>
70 75
71</div> 76</div>
72<h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> 77<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1>
78<div id="EXAMPLE_PROGRAM_CONTENT">
79<pre> #include &lt;ev.h&gt;
80
81 ev_io stdin_watcher;
82 ev_timer timeout_watcher;
83
84 /* called when data readable on stdin */
85 static void
86 stdin_cb (EV_P_ struct ev_io *w, int revents)
87 {
88 /* puts (&quot;stdin ready&quot;); */
89 ev_io_stop (EV_A_ w); /* just a syntax example */
90 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
91 }
92
93 static void
94 timeout_cb (EV_P_ struct ev_timer *w, int revents)
95 {
96 /* puts (&quot;timeout&quot;); */
97 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
98 }
99
100 int
101 main (void)
102 {
103 struct ev_loop *loop = ev_default_loop (0);
104
105 /* initialise an io watcher, then start it */
106 ev_io_init (&amp;stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
107 ev_io_start (loop, &amp;stdin_watcher);
108
109 /* simple non-repeating 5.5 second timeout */
110 ev_timer_init (&amp;timeout_watcher, timeout_cb, 5.5, 0.);
111 ev_timer_start (loop, &amp;timeout_watcher);
112
113 /* loop till timeout or data ready */
114 ev_loop (loop, 0);
115
116 return 0;
117 }
118
119</pre>
120
121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1>
73<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
74<p>Libev is an event loop: you register interest in certain events (such as a 124<p>Libev is an event loop: you register interest in certain events (such as a
75file descriptor being readable or a timeout occuring), and it will manage 125file descriptor being readable or a timeout occuring), and it will manage
76these event sources and provide your program with events.</p> 126these event sources and provide your program with events.</p>
77<p>To do this, it must take more or less complete control over your process 127<p>To do this, it must take more or less complete control over your process
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81watchers</i>, which are relatively small C structures you initialise with the 131watchers</i>, which are relatively small C structures you initialise with the
82details of the event, and then hand it over to libev by <i>starting</i> the 132details of the event, and then hand it over to libev by <i>starting</i> the
83watcher.</p> 133watcher.</p>
84 134
85</div> 135</div>
86<h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> 136<h1 id="FEATURES">FEATURES</h1>
87<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
88<p>Libev supports select, poll, the linux-specific epoll and the bsd-specific 138<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
89kqueue mechanisms for file descriptor events, relative timers, absolute 139BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
90timers with customised rescheduling, signal events, process status change 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
91events (related to SIGCHLD), and event watchers dealing with the event 141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
92loop mechanism itself (idle, prepare and check watchers). It also is quite 142with customised rescheduling (<code>ev_periodic</code>), synchronous signals
143(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
144watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
145<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
146file watchers (<code>ev_stat</code>) and even limited support for fork events
147(<code>ev_fork</code>).</p>
148<p>It also is quite fast (see this
93fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing 149<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
94it to libevent for example).</p> 150for example).</p>
95 151
96</div> 152</div>
97<h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 153<h1 id="CONVENTIONS">CONVENTIONS</h1>
98<div id="CONVENTIONS_CONTENT"> 154<div id="CONVENTIONS_CONTENT">
99<p>Libev is very configurable. In this manual the default configuration 155<p>Libev is very configurable. In this manual the default configuration will
100will be described, which supports multiple event loops. For more info 156be described, which supports multiple event loops. For more info about
101about various configuration options please have a look at the file 157various configuration options please have a look at <strong>EMBED</strong> section in
102<cite>README.embed</cite> in the libev distribution. If libev was configured without 158this manual. If libev was configured without support for multiple event
103support for multiple event loops, then all functions taking an initial 159loops, then all functions taking an initial argument of name <code>loop</code>
104argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 160(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p>
105will not have this argument.</p>
106 161
107</div> 162</div>
108<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 163<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1>
109<div id="TIME_REPRESENTATION_CONTENT"> 164<div id="TIME_REPRESENTATION_CONTENT">
110<p>Libev represents time as a single floating point number, representing the 165<p>Libev represents time as a single floating point number, representing the
111(fractional) number of seconds since the (POSIX) epoch (somewhere near 166(fractional) number of seconds since the (POSIX) epoch (somewhere near
112the beginning of 1970, details are complicated, don't ask). This type is 167the beginning of 1970, details are complicated, don't ask). This type is
113called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 168called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
114to the <code>double</code> type in C, and when you need to do any calculations on 169to the <code>double</code> type in C, and when you need to do any calculations on
115it, you should treat it as such.</p> 170it, you should treat it as such.</p>
116 171
117
118
119
120
121</div> 172</div>
122<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 173<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1>
123<div id="GLOBAL_FUNCTIONS_CONTENT"> 174<div id="GLOBAL_FUNCTIONS_CONTENT">
124<p>These functions can be called anytime, even before initialising the 175<p>These functions can be called anytime, even before initialising the
125library in any way.</p> 176library in any way.</p>
126<dl> 177<dl>
127 <dt>ev_tstamp ev_time ()</dt> 178 <dt>ev_tstamp ev_time ()</dt>
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140version of the library your program was compiled against.</p> 191version of the library your program was compiled against.</p>
141 <p>Usually, it's a good idea to terminate if the major versions mismatch, 192 <p>Usually, it's a good idea to terminate if the major versions mismatch,
142as this indicates an incompatible change. Minor versions are usually 193as this indicates an incompatible change. Minor versions are usually
143compatible to older versions, so a larger minor version alone is usually 194compatible to older versions, so a larger minor version alone is usually
144not a problem.</p> 195not a problem.</p>
145 <p>Example: make sure we haven't accidentally been linked against the wrong 196 <p>Example: Make sure we haven't accidentally been linked against the wrong
146version:</p> 197version.</p>
147<pre> assert ((&quot;libev version mismatch&quot;, 198<pre> assert ((&quot;libev version mismatch&quot;,
148 ev_version_major () == EV_VERSION_MAJOR 199 ev_version_major () == EV_VERSION_MAJOR
149 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR)); 200 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
150 201
151</pre> 202</pre>
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181recommended ones.</p> 232recommended ones.</p>
182 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
183 </dd> 234 </dd>
184 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
185 <dd> 236 <dd>
186 <p>Sets the allocation function to use (the prototype is similar to the 237 <p>Sets the allocation function to use (the prototype is similar - the
187realloc C function, the semantics are identical). It is used to allocate 238semantics is identical - to the realloc C function). It is used to
188and free memory (no surprises here). If it returns zero when memory 239allocate and free memory (no surprises here). If it returns zero when
189needs to be allocated, the library might abort or take some potentially 240memory needs to be allocated, the library might abort or take some
190destructive action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
191 <p>You could override this function in high-availability programs to, say, 243 <p>You could override this function in high-availability programs to, say,
192free some memory if it cannot allocate memory, to use a special allocator, 244free some memory if it cannot allocate memory, to use a special allocator,
193or even to sleep a while and retry until some memory is available.</p> 245or even to sleep a while and retry until some memory is available.</p>
194 <p>Example: replace the libev allocator with one that waits a bit and then 246 <p>Example: Replace the libev allocator with one that waits a bit and then
195retries: better than mine).</p> 247retries).</p>
196<pre> static void * 248<pre> static void *
197 persistent_realloc (void *ptr, long size) 249 persistent_realloc (void *ptr, size_t size)
198 { 250 {
199 for (;;) 251 for (;;)
200 { 252 {
201 void *newptr = realloc (ptr, size); 253 void *newptr = realloc (ptr, size);
202 254
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219indicating the system call or subsystem causing the problem. If this 271indicating the system call or subsystem causing the problem. If this
220callback is set, then libev will expect it to remedy the sitution, no 272callback is set, then libev will expect it to remedy the sitution, no
221matter what, when it returns. That is, libev will generally retry the 273matter what, when it returns. That is, libev will generally retry the
222requested operation, or, if the condition doesn't go away, do bad stuff 274requested operation, or, if the condition doesn't go away, do bad stuff
223(such as abort).</p> 275(such as abort).</p>
224 <p>Example: do the same thing as libev does internally:</p> 276 <p>Example: This is basically the same thing that libev does internally, too.</p>
225<pre> static void 277<pre> static void
226 fatal_error (const char *msg) 278 fatal_error (const char *msg)
227 { 279 {
228 perror (msg); 280 perror (msg);
229 abort (); 281 abort ();
… …
235</pre> 287</pre>
236 </dd> 288 </dd>
237</dl> 289</dl>
238 290
239</div> 291</div>
240<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 292<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1>
241<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 293<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
242<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 294<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
243types of such loops, the <i>default</i> loop, which supports signals and child 295types of such loops, the <i>default</i> loop, which supports signals and child
244events, and dynamically created loops which do not.</p> 296events, and dynamically created loops which do not.</p>
245<p>If you use threads, a common model is to run the default event loop 297<p>If you use threads, a common model is to run the default event loop
… …
365 <dd> 417 <dd>
366 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 418 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
367always distinct from the default loop. Unlike the default loop, it cannot 419always distinct from the default loop. Unlike the default loop, it cannot
368handle signal and child watchers, and attempts to do so will be greeted by 420handle signal and child watchers, and attempts to do so will be greeted by
369undefined behaviour (or a failed assertion if assertions are enabled).</p> 421undefined behaviour (or a failed assertion if assertions are enabled).</p>
370 <p>Example: try to create a event loop that uses epoll and nothing else.</p> 422 <p>Example: Try to create a event loop that uses epoll and nothing else.</p>
371<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 423<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
372 if (!epoller) 424 if (!epoller)
373 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;); 425 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
374 426
375</pre> 427</pre>
… …
468 be handled here by queueing them when their watcher gets executed. 520 be handled here by queueing them when their watcher gets executed.
469 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 521 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
470 were used, return, otherwise continue with step *. 522 were used, return, otherwise continue with step *.
471 523
472</pre> 524</pre>
473 <p>Example: queue some jobs and then loop until no events are outsanding 525 <p>Example: Queue some jobs and then loop until no events are outsanding
474anymore.</p> 526anymore.</p>
475<pre> ... queue jobs here, make sure they register event watchers as long 527<pre> ... queue jobs here, make sure they register event watchers as long
476 ... as they still have work to do (even an idle watcher will do..) 528 ... as they still have work to do (even an idle watcher will do..)
477 ev_loop (my_loop, 0); 529 ev_loop (my_loop, 0);
478 ... jobs done. yeah! 530 ... jobs done. yeah!
… …
497example, libev itself uses this for its internal signal pipe: It is not 549example, libev itself uses this for its internal signal pipe: It is not
498visible to the libev user and should not keep <code>ev_loop</code> from exiting if 550visible to the libev user and should not keep <code>ev_loop</code> from exiting if
499no event watchers registered by it are active. It is also an excellent 551no event watchers registered by it are active. It is also an excellent
500way to do this for generic recurring timers or from within third-party 552way to do this for generic recurring timers or from within third-party
501libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 553libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
502 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> 554 <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code>
503running when nothing else is active.</p> 555running when nothing else is active.</p>
504<pre> struct dv_signal exitsig; 556<pre> struct ev_signal exitsig;
505 ev_signal_init (&amp;exitsig, sig_cb, SIGINT); 557 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
506 ev_signal_start (myloop, &amp;exitsig); 558 ev_signal_start (loop, &amp;exitsig);
507 evf_unref (myloop); 559 evf_unref (loop);
508 560
509</pre> 561</pre>
510 <p>Example: for some weird reason, unregister the above signal handler again.</p> 562 <p>Example: For some weird reason, unregister the above signal handler again.</p>
511<pre> ev_ref (myloop); 563<pre> ev_ref (loop);
512 ev_signal_stop (myloop, &amp;exitsig); 564 ev_signal_stop (loop, &amp;exitsig);
513 565
514</pre> 566</pre>
515 </dd> 567 </dd>
516</dl> 568</dl>
517 569
518 570
519 571
520 572
521 573
522</div> 574</div>
523<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 575<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1>
524<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 576<div id="ANATOMY_OF_A_WATCHER_CONTENT">
525<p>A watcher is a structure that you create and register to record your 577<p>A watcher is a structure that you create and register to record your
526interest in some event. For instance, if you want to wait for STDIN to 578interest in some event. For instance, if you want to wait for STDIN to
527become readable, you would create an <code>ev_io</code> watcher for that:</p> 579become readable, you would create an <code>ev_io</code> watcher for that:</p>
528<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 580<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
… …
585 </dd> 637 </dd>
586 <dt><code>EV_CHILD</code></dt> 638 <dt><code>EV_CHILD</code></dt>
587 <dd> 639 <dd>
588 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> 640 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
589 </dd> 641 </dd>
642 <dt><code>EV_STAT</code></dt>
643 <dd>
644 <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p>
645 </dd>
590 <dt><code>EV_IDLE</code></dt> 646 <dt><code>EV_IDLE</code></dt>
591 <dd> 647 <dd>
592 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> 648 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
593 </dd> 649 </dd>
594 <dt><code>EV_PREPARE</code></dt> 650 <dt><code>EV_PREPARE</code></dt>
… …
599<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 655<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
600received events. Callbacks of both watcher types can start and stop as 656received events. Callbacks of both watcher types can start and stop as
601many watchers as they want, and all of them will be taken into account 657many watchers as they want, and all of them will be taken into account
602(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep 658(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
603<code>ev_loop</code> from blocking).</p> 659<code>ev_loop</code> from blocking).</p>
660 </dd>
661 <dt><code>EV_EMBED</code></dt>
662 <dd>
663 <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p>
664 </dd>
665 <dt><code>EV_FORK</code></dt>
666 <dd>
667 <p>The event loop has been resumed in the child process after fork (see
668<code>ev_fork</code>).</p>
604 </dd> 669 </dd>
605 <dt><code>EV_ERROR</code></dt> 670 <dt><code>EV_ERROR</code></dt>
606 <dd> 671 <dd>
607 <p>An unspecified error has occured, the watcher has been stopped. This might 672 <p>An unspecified error has occured, the watcher has been stopped. This might
608happen because the watcher could not be properly started because libev 673happen because the watcher could not be properly started because libev
… …
678events but its callback has not yet been invoked). As long as a watcher 743events but its callback has not yet been invoked). As long as a watcher
679is pending (but not active) you must not call an init function on it (but 744is pending (but not active) you must not call an init function on it (but
680<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 745<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to
681libev (e.g. you cnanot <code>free ()</code> it).</p> 746libev (e.g. you cnanot <code>free ()</code> it).</p>
682 </dd> 747 </dd>
683 <dt>callback = ev_cb (ev_TYPE *watcher)</dt> 748 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
684 <dd> 749 <dd>
685 <p>Returns the callback currently set on the watcher.</p> 750 <p>Returns the callback currently set on the watcher.</p>
686 </dd> 751 </dd>
687 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 752 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
688 <dd> 753 <dd>
… …
720 struct my_io *w = (struct my_io *)w_; 785 struct my_io *w = (struct my_io *)w_;
721 ... 786 ...
722 } 787 }
723 788
724</pre> 789</pre>
725<p>More interesting and less C-conformant ways of catsing your callback type 790<p>More interesting and less C-conformant ways of casting your callback type
726have been omitted....</p> 791instead have been omitted.</p>
792<p>Another common scenario is having some data structure with multiple
793watchers:</p>
794<pre> struct my_biggy
795 {
796 int some_data;
797 ev_timer t1;
798 ev_timer t2;
799 }
727 800
801</pre>
802<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated,
803you need to use <code>offsetof</code>:</p>
804<pre> #include &lt;stddef.h&gt;
728 805
806 static void
807 t1_cb (EV_P_ struct ev_timer *w, int revents)
808 {
809 struct my_biggy big = (struct my_biggy *
810 (((char *)w) - offsetof (struct my_biggy, t1));
811 }
729 812
813 static void
814 t2_cb (EV_P_ struct ev_timer *w, int revents)
815 {
816 struct my_biggy big = (struct my_biggy *
817 (((char *)w) - offsetof (struct my_biggy, t2));
818 }
730 819
731 820
821
822
823</pre>
824
732</div> 825</div>
733<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 826<h1 id="WATCHER_TYPES">WATCHER TYPES</h1>
734<div id="WATCHER_TYPES_CONTENT"> 827<div id="WATCHER_TYPES_CONTENT">
735<p>This section describes each watcher in detail, but will not repeat 828<p>This section describes each watcher in detail, but will not repeat
736information given in the last section.</p> 829information given in the last section. Any initialisation/set macros,
830functions and members specific to the watcher type are explained.</p>
831<p>Members are additionally marked with either <i>[read-only]</i>, meaning that,
832while the watcher is active, you can look at the member and expect some
833sensible content, but you must not modify it (you can modify it while the
834watcher is stopped to your hearts content), or <i>[read-write]</i>, which
835means you can expect it to have some sensible content while the watcher
836is active, but you can also modify it. Modifying it may not do something
837sensible or take immediate effect (or do anything at all), but libev will
838not crash or malfunction in any way.</p>
737 839
738 840
739 841
740 842
741 843
… …
780 <dd> 882 <dd>
781 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to 883 <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to
782rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or 884rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or
783<code>EV_READ | EV_WRITE</code> to receive the given events.</p> 885<code>EV_READ | EV_WRITE</code> to receive the given events.</p>
784 </dd> 886 </dd>
887 <dt>int fd [read-only]</dt>
888 <dd>
889 <p>The file descriptor being watched.</p>
890 </dd>
891 <dt>int events [read-only]</dt>
892 <dd>
893 <p>The events being watched.</p>
894 </dd>
785</dl> 895</dl>
786<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well 896<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
787readable, but only once. Since it is likely line-buffered, you could 897readable, but only once. Since it is likely line-buffered, you could
788attempt to read a whole line in the callback:</p> 898attempt to read a whole line in the callback.</p>
789<pre> static void 899<pre> static void
790 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 900 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
791 { 901 {
792 ev_io_stop (loop, w); 902 ev_io_stop (loop, w);
793 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors 903 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
… …
846repeating. The exact semantics are:</p> 956repeating. The exact semantics are:</p>
847 <p>If the timer is started but nonrepeating, stop it.</p> 957 <p>If the timer is started but nonrepeating, stop it.</p>
848 <p>If the timer is repeating, either start it if necessary (with the repeat 958 <p>If the timer is repeating, either start it if necessary (with the repeat
849value), or reset the running timer to the repeat value.</p> 959value), or reset the running timer to the repeat value.</p>
850 <p>This sounds a bit complicated, but here is a useful and typical 960 <p>This sounds a bit complicated, but here is a useful and typical
851example: Imagine you have a tcp connection and you want a so-called idle 961example: Imagine you have a tcp connection and you want a so-called
852timeout, that is, you want to be called when there have been, say, 60 962idle timeout, that is, you want to be called when there have been,
853seconds of inactivity on the socket. The easiest way to do this is to 963say, 60 seconds of inactivity on the socket. The easiest way to do
854configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each 964this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
855time you successfully read or write some data. If you go into an idle 965<code>ev_timer_again</code> each time you successfully read or write some data. If
856state where you do not expect data to travel on the socket, you can stop 966you go into an idle state where you do not expect data to travel on the
857the timer, and again will automatically restart it if need be.</p> 967socket, you can stop the timer, and again will automatically restart it if
968need be.</p>
969 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
970and only ever use the <code>repeat</code> value:</p>
971<pre> ev_timer_init (timer, callback, 0., 5.);
972 ev_timer_again (loop, timer);
973 ...
974 timer-&gt;again = 17.;
975 ev_timer_again (loop, timer);
976 ...
977 timer-&gt;again = 10.;
978 ev_timer_again (loop, timer);
979
980</pre>
981 <p>This is more efficient then stopping/starting the timer eahc time you want
982to modify its timeout value.</p>
983 </dd>
984 <dt>ev_tstamp repeat [read-write]</dt>
985 <dd>
986 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
987or <code>ev_timer_again</code> is called and determines the next timeout (if any),
988which is also when any modifications are taken into account.</p>
858 </dd> 989 </dd>
859</dl> 990</dl>
860<p>Example: create a timer that fires after 60 seconds.</p> 991<p>Example: Create a timer that fires after 60 seconds.</p>
861<pre> static void 992<pre> static void
862 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 993 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
863 { 994 {
864 .. one minute over, w is actually stopped right here 995 .. one minute over, w is actually stopped right here
865 } 996 }
… …
867 struct ev_timer mytimer; 998 struct ev_timer mytimer;
868 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.); 999 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
869 ev_timer_start (loop, &amp;mytimer); 1000 ev_timer_start (loop, &amp;mytimer);
870 1001
871</pre> 1002</pre>
872<p>Example: create a timeout timer that times out after 10 seconds of 1003<p>Example: Create a timeout timer that times out after 10 seconds of
873inactivity.</p> 1004inactivity.</p>
874<pre> static void 1005<pre> static void
875 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1006 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
876 { 1007 {
877 .. ten seconds without any activity 1008 .. ten seconds without any activity
… …
980 <p>Simply stops and restarts the periodic watcher again. This is only useful 1111 <p>Simply stops and restarts the periodic watcher again. This is only useful
981when you changed some parameters or the reschedule callback would return 1112when you changed some parameters or the reschedule callback would return
982a different time than the last time it was called (e.g. in a crond like 1113a different time than the last time it was called (e.g. in a crond like
983program when the crontabs have changed).</p> 1114program when the crontabs have changed).</p>
984 </dd> 1115 </dd>
1116 <dt>ev_tstamp interval [read-write]</dt>
1117 <dd>
1118 <p>The current interval value. Can be modified any time, but changes only
1119take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
1120called.</p>
1121 </dd>
1122 <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt>
1123 <dd>
1124 <p>The current reschedule callback, or <code>0</code>, if this functionality is
1125switched off. Can be changed any time, but changes only take effect when
1126the periodic timer fires or <code>ev_periodic_again</code> is being called.</p>
1127 </dd>
985</dl> 1128</dl>
986<p>Example: call a callback every hour, or, more precisely, whenever the 1129<p>Example: Call a callback every hour, or, more precisely, whenever the
987system clock is divisible by 3600. The callback invocation times have 1130system clock is divisible by 3600. The callback invocation times have
988potentially a lot of jittering, but good long-term stability.</p> 1131potentially a lot of jittering, but good long-term stability.</p>
989<pre> static void 1132<pre> static void
990 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1133 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
991 { 1134 {
… …
995 struct ev_periodic hourly_tick; 1138 struct ev_periodic hourly_tick;
996 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0); 1139 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
997 ev_periodic_start (loop, &amp;hourly_tick); 1140 ev_periodic_start (loop, &amp;hourly_tick);
998 1141
999</pre> 1142</pre>
1000<p>Example: the same as above, but use a reschedule callback to do it:</p> 1143<p>Example: The same as above, but use a reschedule callback to do it:</p>
1001<pre> #include &lt;math.h&gt; 1144<pre> #include &lt;math.h&gt;
1002 1145
1003 static ev_tstamp 1146 static ev_tstamp
1004 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1147 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1005 { 1148 {
… …
1007 } 1150 }
1008 1151
1009 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1152 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1010 1153
1011</pre> 1154</pre>
1012<p>Example: call a callback every hour, starting now:</p> 1155<p>Example: Call a callback every hour, starting now:</p>
1013<pre> struct ev_periodic hourly_tick; 1156<pre> struct ev_periodic hourly_tick;
1014 ev_periodic_init (&amp;hourly_tick, clock_cb, 1157 ev_periodic_init (&amp;hourly_tick, clock_cb,
1015 fmod (ev_now (loop), 3600.), 3600., 0); 1158 fmod (ev_now (loop), 3600.), 3600., 0);
1016 ev_periodic_start (loop, &amp;hourly_tick); 1159 ev_periodic_start (loop, &amp;hourly_tick);
1017 1160
… …
1038 <dt>ev_signal_set (ev_signal *, int signum)</dt> 1181 <dt>ev_signal_set (ev_signal *, int signum)</dt>
1039 <dd> 1182 <dd>
1040 <p>Configures the watcher to trigger on the given signal number (usually one 1183 <p>Configures the watcher to trigger on the given signal number (usually one
1041of the <code>SIGxxx</code> constants).</p> 1184of the <code>SIGxxx</code> constants).</p>
1042 </dd> 1185 </dd>
1186 <dt>int signum [read-only]</dt>
1187 <dd>
1188 <p>The signal the watcher watches out for.</p>
1189 </dd>
1043</dl> 1190</dl>
1044 1191
1045 1192
1046 1193
1047 1194
… …
1060at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 1207at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
1061the status word (use the macros from <code>sys/wait.h</code> and see your systems 1208the status word (use the macros from <code>sys/wait.h</code> and see your systems
1062<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 1209<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
1063process causing the status change.</p> 1210process causing the status change.</p>
1064 </dd> 1211 </dd>
1212 <dt>int pid [read-only]</dt>
1213 <dd>
1214 <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p>
1215 </dd>
1216 <dt>int rpid [read-write]</dt>
1217 <dd>
1218 <p>The process id that detected a status change.</p>
1219 </dd>
1220 <dt>int rstatus [read-write]</dt>
1221 <dd>
1222 <p>The process exit/trace status caused by <code>rpid</code> (see your systems
1223<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p>
1224 </dd>
1065</dl> 1225</dl>
1066<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> 1226<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p>
1067<pre> static void 1227<pre> static void
1068 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1228 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1069 { 1229 {
1070 ev_unloop (loop, EVUNLOOP_ALL); 1230 ev_unloop (loop, EVUNLOOP_ALL);
1071 } 1231 }
1072 1232
1073 struct ev_signal signal_watcher; 1233 struct ev_signal signal_watcher;
1074 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT); 1234 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
1075 ev_signal_start (loop, &amp;sigint_cb); 1235 ev_signal_start (loop, &amp;sigint_cb);
1236
1237
1238
1239
1240</pre>
1241
1242</div>
1243<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2>
1244<div id="code_ev_stat_code_did_the_file_attri-2">
1245<p>This watches a filesystem path for attribute changes. That is, it calls
1246<code>stat</code> regularly (or when the OS says it changed) and sees if it changed
1247compared to the last time, invoking the callback if it did.</p>
1248<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1249not exist&quot; is a status change like any other. The condition &quot;path does
1250not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1251otherwise always forced to be at least one) and all the other fields of
1252the stat buffer having unspecified contents.</p>
1253<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1254relative and your working directory changes, the behaviour is undefined.</p>
1255<p>Since there is no standard to do this, the portable implementation simply
1256calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1257can specify a recommended polling interval for this case. If you specify
1258a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1259unspecified default</i> value will be used (which you can expect to be around
1260five seconds, although this might change dynamically). Libev will also
1261impose a minimum interval which is currently around <code>0.1</code>, but thats
1262usually overkill.</p>
1263<p>This watcher type is not meant for massive numbers of stat watchers,
1264as even with OS-supported change notifications, this can be
1265resource-intensive.</p>
1266<p>At the time of this writing, only the Linux inotify interface is
1267implemented (implementing kqueue support is left as an exercise for the
1268reader). Inotify will be used to give hints only and should not change the
1269semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs
1270to fall back to regular polling again even with inotify, but changes are
1271usually detected immediately, and if the file exists there will be no
1272polling.</p>
1273<dl>
1274 <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt>
1275 <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt>
1276 <dd>
1277 <p>Configures the watcher to wait for status changes of the given
1278<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to
1279be detected and should normally be specified as <code>0</code> to let libev choose
1280a suitable value. The memory pointed to by <code>path</code> must point to the same
1281path for as long as the watcher is active.</p>
1282 <p>The callback will be receive <code>EV_STAT</code> when a change was detected,
1283relative to the attributes at the time the watcher was started (or the
1284last change was detected).</p>
1285 </dd>
1286 <dt>ev_stat_stat (ev_stat *)</dt>
1287 <dd>
1288 <p>Updates the stat buffer immediately with new values. If you change the
1289watched path in your callback, you could call this fucntion to avoid
1290detecting this change (while introducing a race condition). Can also be
1291useful simply to find out the new values.</p>
1292 </dd>
1293 <dt>ev_statdata attr [read-only]</dt>
1294 <dd>
1295 <p>The most-recently detected attributes of the file. Although the type is of
1296<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types
1297suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there
1298was some error while <code>stat</code>ing the file.</p>
1299 </dd>
1300 <dt>ev_statdata prev [read-only]</dt>
1301 <dd>
1302 <p>The previous attributes of the file. The callback gets invoked whenever
1303<code>prev</code> != <code>attr</code>.</p>
1304 </dd>
1305 <dt>ev_tstamp interval [read-only]</dt>
1306 <dd>
1307 <p>The specified interval.</p>
1308 </dd>
1309 <dt>const char *path [read-only]</dt>
1310 <dd>
1311 <p>The filesystem path that is being watched.</p>
1312 </dd>
1313</dl>
1314<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p>
1315<pre> static void
1316 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1317 {
1318 /* /etc/passwd changed in some way */
1319 if (w-&gt;attr.st_nlink)
1320 {
1321 printf (&quot;passwd current size %ld\n&quot;, (long)w-&gt;attr.st_size);
1322 printf (&quot;passwd current atime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1323 printf (&quot;passwd current mtime %ld\n&quot;, (long)w-&gt;attr.st_mtime);
1324 }
1325 else
1326 /* you shalt not abuse printf for puts */
1327 puts (&quot;wow, /etc/passwd is not there, expect problems. &quot;
1328 &quot;if this is windows, they already arrived\n&quot;);
1329 }
1330
1331 ...
1332 ev_stat passwd;
1333
1334 ev_stat_init (&amp;passwd, passwd_cb, &quot;/etc/passwd&quot;);
1335 ev_stat_start (loop, &amp;passwd);
1076 1336
1077 1337
1078 1338
1079 1339
1080</pre> 1340</pre>
… …
1101 <p>Initialises and configures the idle watcher - it has no parameters of any 1361 <p>Initialises and configures the idle watcher - it has no parameters of any
1102kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 1362kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
1103believe me.</p> 1363believe me.</p>
1104 </dd> 1364 </dd>
1105</dl> 1365</dl>
1106<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the 1366<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the
1107callback, free it. Alos, use no error checking, as usual.</p> 1367callback, free it. Also, use no error checking, as usual.</p>
1108<pre> static void 1368<pre> static void
1109 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1369 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1110 { 1370 {
1111 free (w); 1371 free (w);
1112 // now do something you wanted to do when the program has 1372 // now do something you wanted to do when the program has
… …
1126<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2> 1386<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
1127<div id="code_ev_prepare_code_and_code_ev_che-2"> 1387<div id="code_ev_prepare_code_and_code_ev_che-2">
1128<p>Prepare and check watchers are usually (but not always) used in tandem: 1388<p>Prepare and check watchers are usually (but not always) used in tandem:
1129prepare watchers get invoked before the process blocks and check watchers 1389prepare watchers get invoked before the process blocks and check watchers
1130afterwards.</p> 1390afterwards.</p>
1391<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
1392the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
1393watchers. Other loops than the current one are fine, however. The
1394rationale behind this is that you do not need to check for recursion in
1395those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
1396<code>ev_check</code> so if you have one watcher of each kind they will always be
1397called in pairs bracketing the blocking call.</p>
1131<p>Their main purpose is to integrate other event mechanisms into libev and 1398<p>Their main purpose is to integrate other event mechanisms into libev and
1132their use is somewhat advanced. This could be used, for example, to track 1399their use is somewhat advanced. This could be used, for example, to track
1133variable changes, implement your own watchers, integrate net-snmp or a 1400variable changes, implement your own watchers, integrate net-snmp or a
1134coroutine library and lots more.</p> 1401coroutine library and lots more. They are also occasionally useful if
1402you cache some data and want to flush it before blocking (for example,
1403in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
1404watcher).</p>
1135<p>This is done by examining in each prepare call which file descriptors need 1405<p>This is done by examining in each prepare call which file descriptors need
1136to be watched by the other library, registering <code>ev_io</code> watchers for 1406to be watched by the other library, registering <code>ev_io</code> watchers for
1137them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1407them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
1138provide just this functionality). Then, in the check watcher you check for 1408provide just this functionality). Then, in the check watcher you check for
1139any events that occured (by checking the pending status of all watchers 1409any events that occured (by checking the pending status of all watchers
… …
1155 <p>Initialises and configures the prepare or check watcher - they have no 1425 <p>Initialises and configures the prepare or check watcher - they have no
1156parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1426parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1157macros, but using them is utterly, utterly and completely pointless.</p> 1427macros, but using them is utterly, utterly and completely pointless.</p>
1158 </dd> 1428 </dd>
1159</dl> 1429</dl>
1160<p>Example: *TODO*.</p> 1430<p>Example: To include a library such as adns, you would add IO watchers
1431and a timeout watcher in a prepare handler, as required by libadns, and
1432in a check watcher, destroy them and call into libadns. What follows is
1433pseudo-code only of course:</p>
1434<pre> static ev_io iow [nfd];
1435 static ev_timer tw;
1161 1436
1437 static void
1438 io_cb (ev_loop *loop, ev_io *w, int revents)
1439 {
1440 // set the relevant poll flags
1441 // could also call adns_processreadable etc. here
1442 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1443 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1444 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1445 }
1162 1446
1447 // create io watchers for each fd and a timer before blocking
1448 static void
1449 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1450 {
1451 int timeout = 3600000;truct pollfd fds [nfd];
1452 // actual code will need to loop here and realloc etc.
1453 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1163 1454
1455 /* the callback is illegal, but won't be called as we stop during check */
1456 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1457 ev_timer_start (loop, &amp;tw);
1164 1458
1459 // create on ev_io per pollfd
1460 for (int i = 0; i &lt; nfd; ++i)
1461 {
1462 ev_io_init (iow + i, io_cb, fds [i].fd,
1463 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1464 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1465
1466 fds [i].revents = 0;
1467 iow [i].data = fds + i;
1468 ev_io_start (loop, iow + i);
1469 }
1470 }
1471
1472 // stop all watchers after blocking
1473 static void
1474 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1475 {
1476 ev_timer_stop (loop, &amp;tw);
1477
1478 for (int i = 0; i &lt; nfd; ++i)
1479 ev_io_stop (loop, iow + i);
1480
1481 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1482 }
1483
1484
1485
1486
1487</pre>
1165 1488
1166</div> 1489</div>
1167<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2> 1490<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
1168<div id="code_ev_embed_code_when_one_backend_-2"> 1491<div id="code_ev_embed_code_when_one_backend_-2">
1169<p>This is a rather advanced watcher type that lets you embed one event loop 1492<p>This is a rather advanced watcher type that lets you embed one event loop
… …
1240 <dd> 1563 <dd>
1241 <p>Make a single, non-blocking sweep over the embedded loop. This works 1564 <p>Make a single, non-blocking sweep over the embedded loop. This works
1242similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most 1565similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most
1243apropriate way for embedded loops.</p> 1566apropriate way for embedded loops.</p>
1244 </dd> 1567 </dd>
1568 <dt>struct ev_loop *loop [read-only]</dt>
1569 <dd>
1570 <p>The embedded event loop.</p>
1571 </dd>
1245</dl> 1572</dl>
1246 1573
1247 1574
1248 1575
1249 1576
1250 1577
1251</div> 1578</div>
1252<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1579<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2>
1580<div id="code_ev_fork_code_the_audacity_to_re-2">
1581<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because
1582whoever is a good citizen cared to tell libev about it by calling
1583<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the
1584event loop blocks next and before <code>ev_check</code> watchers are being called,
1585and only in the child after the fork. If whoever good citizen calling
1586<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork
1587handlers will be invoked, too, of course.</p>
1588<dl>
1589 <dt>ev_fork_init (ev_signal *, callback)</dt>
1590 <dd>
1591 <p>Initialises and configures the fork watcher - it has no parameters of any
1592kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless,
1593believe me.</p>
1594 </dd>
1595</dl>
1596
1597
1598
1599
1600
1601</div>
1602<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1>
1253<div id="OTHER_FUNCTIONS_CONTENT"> 1603<div id="OTHER_FUNCTIONS_CONTENT">
1254<p>There are some other functions of possible interest. Described. Here. Now.</p> 1604<p>There are some other functions of possible interest. Described. Here. Now.</p>
1255<dl> 1605<dl>
1256 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1606 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
1257 <dd> 1607 <dd>
… …
1304 1654
1305 1655
1306 1656
1307 1657
1308</div> 1658</div>
1309<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> 1659<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1>
1310<div id="LIBEVENT_EMULATION_CONTENT"> 1660<div id="LIBEVENT_EMULATION_CONTENT">
1311<p>Libev offers a compatibility emulation layer for libevent. It cannot 1661<p>Libev offers a compatibility emulation layer for libevent. It cannot
1312emulate the internals of libevent, so here are some usage hints:</p> 1662emulate the internals of libevent, so here are some usage hints:</p>
1313<dl> 1663<dl>
1314 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt> 1664 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
… …
1324 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need 1674 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1325to use the libev header file and library.</dt> 1675to use the libev header file and library.</dt>
1326</dl> 1676</dl>
1327 1677
1328</div> 1678</div>
1329<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> 1679<h1 id="C_SUPPORT">C++ SUPPORT</h1>
1330<div id="C_SUPPORT_CONTENT"> 1680<div id="C_SUPPORT_CONTENT">
1331<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow 1681<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow
1332you to use some convinience methods to start/stop watchers and also change 1682you to use some convinience methods to start/stop watchers and also change
1333the callback model to a model using method callbacks on objects.</p> 1683the callback model to a model using method callbacks on objects.</p>
1334<p>To use it,</p> 1684<p>To use it,</p>
… …
1398 </dd> 1748 </dd>
1399 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt> 1749 <dt>w-&gt;sweep () <code>ev::embed</code> only</dt>
1400 <dd> 1750 <dd>
1401 <p>Invokes <code>ev_embed_sweep</code>.</p> 1751 <p>Invokes <code>ev_embed_sweep</code>.</p>
1402 </dd> 1752 </dd>
1753 <dt>w-&gt;update () <code>ev::stat</code> only</dt>
1754 <dd>
1755 <p>Invokes <code>ev_stat_stat</code>.</p>
1756 </dd>
1403 </dl> 1757 </dl>
1404 </p> 1758 </p>
1405 </dd> 1759 </dd>
1406</dl> 1760</dl>
1407<p>Example: Define a class with an IO and idle watcher, start one of them in 1761<p>Example: Define a class with an IO and idle watcher, start one of them in
… …
1419 idle (this, &amp;myclass::idle_cb) 1773 idle (this, &amp;myclass::idle_cb)
1420 { 1774 {
1421 io.start (fd, ev::READ); 1775 io.start (fd, ev::READ);
1422 } 1776 }
1423 1777
1424</pre>
1425 1778
1779
1780
1781</pre>
1782
1426</div> 1783</div>
1427<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p> 1784<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1785<div id="MACRO_MAGIC_CONTENT">
1786<p>Libev can be compiled with a variety of options, the most fundemantal is
1787<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
1788callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1789<p>To make it easier to write programs that cope with either variant, the
1790following macros are defined:</p>
1791<dl>
1792 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
1793 <dd>
1794 <p>This provides the loop <i>argument</i> for functions, if one is required (&quot;ev
1795loop argument&quot;). The <code>EV_A</code> form is used when this is the sole argument,
1796<code>EV_A_</code> is used when other arguments are following. Example:</p>
1797<pre> ev_unref (EV_A);
1798 ev_timer_add (EV_A_ watcher);
1799 ev_loop (EV_A_ 0);
1800
1801</pre>
1802 <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope,
1803which is often provided by the following macro.</p>
1804 </dd>
1805 <dt><code>EV_P</code>, <code>EV_P_</code></dt>
1806 <dd>
1807 <p>This provides the loop <i>parameter</i> for functions, if one is required (&quot;ev
1808loop parameter&quot;). The <code>EV_P</code> form is used when this is the sole parameter,
1809<code>EV_P_</code> is used when other parameters are following. Example:</p>
1810<pre> // this is how ev_unref is being declared
1811 static void ev_unref (EV_P);
1812
1813 // this is how you can declare your typical callback
1814 static void cb (EV_P_ ev_timer *w, int revents)
1815
1816</pre>
1817 <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite
1818suitable for use with <code>EV_A</code>.</p>
1819 </dd>
1820 <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt>
1821 <dd>
1822 <p>Similar to the other two macros, this gives you the value of the default
1823loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1824 </dd>
1825</dl>
1826<p>Example: Declare and initialise a check watcher, working regardless of
1827wether multiple loops are supported or not.</p>
1828<pre> static void
1829 check_cb (EV_P_ ev_timer *w, int revents)
1830 {
1831 ev_check_stop (EV_A_ w);
1832 }
1833
1834 ev_check check;
1835 ev_check_init (&amp;check, check_cb);
1836 ev_check_start (EV_DEFAULT_ &amp;check);
1837 ev_loop (EV_DEFAULT_ 0);
1838
1839
1840
1841
1842</pre>
1843
1844</div>
1845<h1 id="EMBEDDING">EMBEDDING</h1>
1428<div id="EMBEDDING_CONTENT"> 1846<div id="EMBEDDING_CONTENT">
1429<p>Libev can (and often is) directly embedded into host 1847<p>Libev can (and often is) directly embedded into host
1430applications. Examples of applications that embed it include the Deliantra 1848applications. Examples of applications that embed it include the Deliantra
1431Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 1849Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1432and rxvt-unicode.</p> 1850and rxvt-unicode.</p>
… …
1606 </dd> 2024 </dd>
1607 <dt>EV_USE_DEVPOLL</dt> 2025 <dt>EV_USE_DEVPOLL</dt>
1608 <dd> 2026 <dd>
1609 <p>reserved for future expansion, works like the USE symbols above.</p> 2027 <p>reserved for future expansion, works like the USE symbols above.</p>
1610 </dd> 2028 </dd>
2029 <dt>EV_USE_INOTIFY</dt>
2030 <dd>
2031 <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify
2032interface to speed up <code>ev_stat</code> watchers. Its actual availability will
2033be detected at runtime.</p>
2034 </dd>
1611 <dt>EV_H</dt> 2035 <dt>EV_H</dt>
1612 <dd> 2036 <dd>
1613 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if 2037 <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
1614undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This 2038undefined is <code>&lt;ev.h&gt;</code> in <cite>event.h</cite> and <code>&quot;ev.h&quot;</code> in <cite>ev.c</cite>. This
1615can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> 2039can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
… …
1638will have the <code>struct ev_loop *</code> as first argument, and you can create 2062will have the <code>struct ev_loop *</code> as first argument, and you can create
1639additional independent event loops. Otherwise there will be no support 2063additional independent event loops. Otherwise there will be no support
1640for multiple event loops and there is no first event loop pointer 2064for multiple event loops and there is no first event loop pointer
1641argument. Instead, all functions act on the single default loop.</p> 2065argument. Instead, all functions act on the single default loop.</p>
1642 </dd> 2066 </dd>
1643 <dt>EV_PERIODICS</dt> 2067 <dt>EV_PERIODIC_ENABLE</dt>
1644 <dd> 2068 <dd>
1645 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported, 2069 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
1646otherwise not. This saves a few kb of code.</p> 2070defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2071code.</p>
2072 </dd>
2073 <dt>EV_EMBED_ENABLE</dt>
2074 <dd>
2075 <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If
2076defined to be <code>0</code>, then they are not.</p>
2077 </dd>
2078 <dt>EV_STAT_ENABLE</dt>
2079 <dd>
2080 <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If
2081defined to be <code>0</code>, then they are not.</p>
2082 </dd>
2083 <dt>EV_FORK_ENABLE</dt>
2084 <dd>
2085 <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If
2086defined to be <code>0</code>, then they are not.</p>
2087 </dd>
2088 <dt>EV_MINIMAL</dt>
2089 <dd>
2090 <p>If you need to shave off some kilobytes of code at the expense of some
2091speed, define this symbol to <code>1</code>. Currently only used for gcc to override
2092some inlining decisions, saves roughly 30% codesize of amd64.</p>
2093 </dd>
2094 <dt>EV_PID_HASHSIZE</dt>
2095 <dd>
2096 <p><code>ev_child</code> watchers use a small hash table to distribute workload by
2097pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more
2098than enough. If you need to manage thousands of children you might want to
2099increase this value (<i>must</i> be a power of two).</p>
2100 </dd>
2101 <dt>EV_INOTIFY_HASHSIZE</dt>
2102 <dd>
2103 <p><code>ev_staz</code> watchers use a small hash table to distribute workload by
2104inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>),
2105usually more than enough. If you need to manage thousands of <code>ev_stat</code>
2106watchers you might want to increase this value (<i>must</i> be a power of
2107two).</p>
1647 </dd> 2108 </dd>
1648 <dt>EV_COMMON</dt> 2109 <dt>EV_COMMON</dt>
1649 <dd> 2110 <dd>
1650 <p>By default, all watchers have a <code>void *data</code> member. By redefining 2111 <p>By default, all watchers have a <code>void *data</code> member. By redefining
1651this macro to a something else you can include more and other types of 2112this macro to a something else you can include more and other types of
… …
1691</pre> 2152</pre>
1692 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2153 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
1693<pre> #include &quot;ev_cpp.h&quot; 2154<pre> #include &quot;ev_cpp.h&quot;
1694 #include &quot;ev.c&quot; 2155 #include &quot;ev.c&quot;
1695 2156
1696</pre>
1697 2157
2158
2159
2160</pre>
2161
1698</div> 2162</div>
1699<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 2163<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2164<div id="COMPLEXITIES_CONTENT">
2165 <p>In this section the complexities of (many of) the algorithms used inside
2166libev will be explained. For complexity discussions about backends see the
2167documentation for <code>ev_default_init</code>.</p>
2168 <p>
2169 <dl>
2170 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2171 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2172 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2173 <dt>Stopping check/prepare/idle watchers: O(1)</dt>
2174 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2175 <dt>Finding the next timer per loop iteration: O(1)</dt>
2176 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2177 <dt>Activating one watcher: O(1)</dt>
2178 </dl>
2179 </p>
2180
2181
2182
2183
2184
2185</div>
2186<h1 id="AUTHOR">AUTHOR</h1>
1700<div id="AUTHOR_CONTENT"> 2187<div id="AUTHOR_CONTENT">
1701 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 2188 <p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
1702 2189
1703</div> 2190</div>
1704</div></body> 2191</div></body>

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